1. Field of the Invention
This invention relates generally to a photographic apparatus with a quench flash for providing a proportional fill-in flash, and more particularly, to a photographic system for controlling the firing of an electronic flash of the quench type under conditions of either substantial or negligible ambient scene light so that the flash contributes a predetermined proportion of the exposure under conditions of substantial ambient scene light intensity.
2. Description of the Prior Art
In the photographic art, exposure control systems embodying scanning shutter blade elements which operate to vary the exposure aperture areas with time during the exposure interval are well known as indicated by U.S. Pat. No. 3,942,183, entitled "Camera with Pivoting Blades", by G. Whiteside, issued Mar. 2, 1976, in common assignment herewith. Such scanning shutter blade mechanisms generally include a pair of counter-reciprocating shutter blade elements each having a primary aperture that transverses the optical axis of the camera during the exposure interval. The primary apertures are shaped so that upon overlying one another during countermovement of the blades, there is defined an effective exposure aperture value which increases to a maximum value in a determinate period of time.
Exposure control is provided by a pair of secondary photocell apertures is respective shutter blade elements which admit scene light to a photoresponsive element in correspondence with the scene light admitted to the focal plane during shutter blade movement through an exposure cycle. The output from the photoresponsive element is directed to an integration circuit which triggers upon reaching an integration level corresponding to a desired exposure value to terminate the exposure interval by returning the shutter blade elements back to their initial scene light blocking position.
Such exposure control systems may be utilized with a source of artificial illumination such as a flashbulb or electronic flash to provide artificial illumination not only during conditions of low ambient scene light intensity but also under conditions of high ambient scene light intensity wherein it becomes desirable to provide the artificial illumination to fill in the photographic subject against a brightly back lit scene as is more fully disclosed in U.S. Pat. No. 4,023,187, entitled "Exposure Control System with Fill Flash Race Condition", by E. Shenk, issued May 10, 1977, in common assignment herewith. The aforementioned artificial illumination control system operates under conditions of low ambient scene light intensity to fire the source of artificial illumination at a predetermined time period subsequent to the initiation of the exposure interval and under conditions of high ambient scene light intensity to fire the source of artificial illumination as a consequence of the time integration of the scene light intensity incident to the photoresponsive element reaching a predetermined value. Although the aforementioned artificial illumination control system performs in a highly satisfactory manner, it nevertheless fails to provide a select ratio or proportion between that part of the exposure which is directly attributable to the artificial scene illumination and the remaining part of the exposure which is directly attributable to ambient scene light illumination over a determinate range of camera-to-subject distances.
Such a proportional fill flash, however, has been provided in an automatic fashion in a manner as is described in U.S. Patent Application Ser. No. 960,062, entitled "Proportional Fill Flash", by A. LaRocque et al., filed Nov. 13, 1978, now U.S. Pat. No. 4,150,891 in common assignment herewith. A proportional fill flash is provided by the aforementioned system by utilizing a sonar ranging device to initially determine the camera-to-subject range and to thereafter utilize the ranging information to vary the time in which the flash is fired during the opening shutter blade movement so as to fire the flash at the appropriate aperture corresponding to the camera-to-subject range. Such a system, however, is complex and must embody some means for determining camera-to-subject range such as the aforementioned sonar range finder.
Therefore, it is a primary object of this invention to provide a photographic exposure control system for providing a proportional fill flash in a simple and economic manner utilizing an electronic flash of the quench type without a range finding device.
It is a further object of this invention to provide a simple and economic exposure control system for providing a proportional fill flash by firing and quenching an electronic flash of the quench type at the appropriate time during a photographic exposure cycle without determining the exact camera-to-subject distance.
Other objects of the invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises a mechanism and system possessing a construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.